Rate constants for the reactions of methylvinyl ketone, methacrolein, methacrylic acid, and acrylic acid with ozone

Abstract

Rate constants for the reaction of ozone with methylvinyl ketone (H 2 C " CHC(O)CH 3 ), methacrolein (H 2 C" C(CH 3 )CHO), methacrylic acid (H 2 C "C(CH 3 )C(O)OH), and acrylic acid (H 2 C " CHC(O)OH) were measured at room temperature in the pres-(296 Ϯ 2 K) ence of a sufficient amount of cyclohexane to scavenge OH-radicals. Results from pseudofirst-order experiments in the presence of excess ozone were found not to be consistent with relative rate measurements. It appeared that the formation of the so-called Criegee-intermediates leads to an enhanced decrease in the concentration of the two organic acids investigated. It is shown that the presence of formic acid, which is known to react efficiently with Criegee-intermediates, diminishes the observed removal rate of the organic acids. The rate constant for the reaction of ozone with the unsaturated carbonyl compounds methylvinyl ketone and methacrolein was found not to be influenced by the addition of formic acid. Rate constants for the reaction of ozone determined in the presence of excess formic acid are (in ): methylvinyl ketone methacrolein 3 Ϫ1 Ϫ1 Ϫ18

The stable-carbon kinetic isotope effects of the reactions of isoprene, methacrolein, and methyl vinyl ketone with ozone in the gas phase

“…The average k RR value for MACR, (1.9 ± 0.12) × 10 -18 cm 3 molecule -1 s -1 , is about 50-75% higher than the four rate constants for this reaction reported by Grosjean et al (1993) [(1.02 ± 0.05) × 10 -18 ], Grosjean and Grosjean (1998) [(1.08 ± 0.21) × 10 -18 ], Atkinson et al (1981) [(1.12 ± 0.13) × 10 -18 ], and Neeb et al (1998) [(1.30 ± 0.14) × 10 -18 ], all in units of cm 3 molecule -1 s -1 . That our experimental rate constant for MACR is higher than other reported values, with rate constants for all other VOCs in agreement with literature, suggests that there are additional processes removing MACR.…”

Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach

“…This method was extended to conjugated dienes (see Table 3). Evaluations for unsaturated carbonyl were based on the following rate constants at room temperature (in molecule −1 cm 3 s −1 units): (Atkinson, 1994); -methyl vinyl ketone: k=5.4×10 −18 (Neeb et al, 1998) -methacrolein: k=1.1×10 −18 (Atkinson, 1994) -crotonaldehyde: k=1.7×10 −18 (Grosjean and Grosjean, 1998) Rates for acrolein and methyl vinyl ketone were used as generic constants for unsaturated aldehydes and ketones, respectively. Contribution of alkyl groups in α and β positions relative to the carbonyl were taken into account using an enhancement factor of 3.9 and 6.0, respectively, based on the rate constant ratio of methacrolein and crotonaldehyde with respect to acrolein.…”

Mechanism and Kinetics of Heterogeneous Reactions of Unsaturated Organic Acids on α‐Al2O3 and CaCO3

“…It is generally accepted that unsaturated organic acids show high reactivity in homogeneous reactions with typical atmospheric oxidants due to the existence of carbon–carbon double bonds in their structures. Previous studies suggest that the tropospheric lifetimes for unsaturated organic acids due to reaction with OH radicals are of the order of a few hours and can represent the dominant atmospheric sink process . It should be noted that under high‐pollution events, the lifetimes of acrylic acid and methacrylic acid resulting from uptake on mineral oxides are calculated to be in the range 4.6–11.1 h, which are comparable to those caused by OH oxidation (3.4–8 h) and are much shorter than those caused by ozonolysis of unsaturated organic acids (4.0–25 d).…”

“…The concentration of OH used in this calculation was 2×10 6 molecules cm −3 . [d] The rate coefficient was calculated from reference . The concentration of O 3 used in this calculation was 7×10 11 molecules cm −3 …”